So the OP hasn't replied. I truly hope that she has come and read this thread. Please neuter your cat. I guarantee you can find a shelter kitten that will more than amply fill your wonderful kitties footprints. You will never, no matter what you try, replace your cat 100%, like humans each are individuals. Even identical twins can have separate personalities. Your boy will spray, he will howl, and the female will return. It's actually a terribly selfish thing you are doing here. For your peace of mind and sleep, and your neighbours, you really should be considering neutering. It will solve your problem.